JP2017072441A - X-ray imaging device and x-ray imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray imaging device and X-ray imaging method that can easily observe samples as selecting energy regions of an X-ray.SOLUTION: An X-ray imaging device 10A comprises: an X-ray source 1; a detector 7; a converging optical system 3A that includes a first reflection surface 31c and second reflection surface 32c for allowing total reflection to converge an X-ray 20 emitted from the X-ray source 1 to a sample S; an image formation optical system 6; and a control unit that conducts control of switching a state of the converging optical system 3A between a first state where the X-ray 20 totally reflected upon the first reflection surface 31c is converged to the sample S and a second state where the X-ray 20 totally reflected upon the second reflection surface 32c is converged to the sample S. A first inclination angle α1 and second inclination angle α2 are mutually different, and an angle γ formed with an optical axis of the X-ray 20 totally reflected upon the first reflection surface 31c in the first state and a reference line A and an angle γ formed with an optical angle of the X-ray 20 totally reflected upon the second reflection surface 32c in the second state are mutually equal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an X-ray imaging apparatus and an X-ray imaging method.

  The X-ray absorption coefficient varies depending on the energy of X-rays even for the same substance. Therefore, in the X-ray imaging apparatus, the X-ray energy region to be used is selected according to the constituent material of the sample. For example, Patent Document 1 describes a light collecting device including an aspherical mirror and a vent mechanism. The vent mechanism selects the radius of curvature of the aspherical mirror in the longitudinal direction according to the energy of the X-rays by adjusting the longitudinal deflection of the aspherical mirror.

  Patent Documents 2 and 3 describe an X-ray microscope. The X-ray microscope described in Patent Document 3 includes an illumination optical system having two reflection regions with different reflection angles in the optical axis direction, and a moving unit that moves the illumination optical system in the optical axis direction. In this X-ray microscope, the bright field observation mode and the dark field observation mode can be switched by moving the illumination optical system in the optical axis direction.

JP 2014-163667 A JP 2008-96273 A JP 2006-343535 A

  In the condensing device described in Patent Document 1, the incident angle of X-rays to the sample changes according to the energy of X-rays. Therefore, when the imaging optical system and the detector are provided behind the sample, the X-ray from the sample is imaged on the detector by the imaging optical system in accordance with the selected X-ray energy. It is necessary to align the optical system and the detector. Note that the X-ray microscope described in Patent Document 3 does not mention selecting X-ray energy.

  An object of the present invention is to provide an X-ray imaging apparatus and an X-ray imaging method capable of easily observing a sample while selecting an X-ray energy region.

  An X-ray imaging apparatus according to the present invention is disposed on an X-ray source that emits X-rays that irradiate a sample, a detector that detects X-rays from the sample, and a reference line from the X-ray source to the detector, A condensing optical system having a first reflecting surface and a second reflecting surface for condensing the X-ray emitted from the X-ray source onto the sample by total reflection, and the X-ray from the sample are arranged on the reference line. The imaging optical system that forms an image on the vessel and the state of the condensing optical system are the first state in which the X-rays totally reflected on the first reflecting surface are condensed on the sample, and the second reflecting surface is totally reflected. A control unit that performs control to switch between the second state in which the X-rays are collected on the sample, and the sample is held at a predetermined distance from the X-ray source on the reference line. The angle formed between the reflection surface and the reference line is different from the angle formed between the second reflection surface and the reference line, and the first reflection in the first state. The angle formed by the optical axis of the X-rays totally reflected by the reference line and the reference line is equal to the angle formed by the optical axis of the X-rays totally reflected by the second reflecting surface in the second state and the reference line. is there.

  This X-ray imaging apparatus includes a control unit that switches the state of the condensing optical system. The control unit switches between a first state in which X-rays are totally reflected by the first reflecting surface and enter the sample, and a second state in which X-rays are totally reflected by the second reflecting surface and enter the sample. The angle formed between the first reflecting surface and the reference line is different from the angle formed between the second reflecting surface and the reference line. Further, in the first state, an angle formed between the optical axis of the X-rays totally reflected by the first reflecting surface and the reference line, and in the second state, an optical axis of the X-rays totally reflected by the second reflecting surface; The angles formed with the reference line are equal to each other. Therefore, the oblique incident angle of the X-rays to the first reflecting surface in the first state and the oblique incident angle of the X-rays to the second reflecting surface in the second state are different from each other due to a geometric relationship. When the oblique incident angle of X-rays to the reflecting surface is different, the energy region of X-rays totally reflected by the reflecting surface is different. Thereby, by switching between the first state and the second state, X-rays used for observation of the sample are totally reflected by the first reflecting surface and the energy that is totally reflected by the second reflecting surface. The region can be selected from the X-rays. As described above, in the first state and the second state, the angle formed between the optical axis of the X-ray totally reflected by the first reflecting surface and the reference line, and the X-ray light totally reflected by the second reflecting surface. The angles formed by the axis and the reference line are equal to each other. For this reason, the incident state of the X-rays to the imaging optical system does not change between the first state and the second state. Therefore, it is not necessary to align the imaging optical system and the detector according to the selection of the X-ray energy. As described above, in this X-ray imaging apparatus, a sample can be easily observed while selecting an X-ray energy region.

  In this X-ray imaging device, the first optical element including the first reflecting surface and the second reflecting surface are integrated with the first optical element in a state of being aligned with the first optical element along the reference line. The control unit may switch between the first state and the second state by moving the first optical element and the second optical element along the reference line. In this case, since the first optical element and the second optical element are integrated, the state of the condensing optical system can be switched by moving the first optical element and the second optical element by a common moving mechanism. .

  In this X-ray imaging apparatus, the condensing optical system includes a first optical element including a first reflecting surface, and a second optical element including a second reflecting surface and configured separately from the first optical element. The control unit may switch between the first state and the second state by moving the first optical element and the second optical element. In this case, since the first optical element and the second optical element are configured separately, the first optical element and the second optical element can be moved. Therefore, the first optical element and the second optical element can be easily arranged at a position for condensing the X-ray emitted from the X-ray source on the sample by total reflection.

  In this X-ray imaging apparatus, a first shielding member for shielding X-rays from the X-ray source toward the second reflecting surface, and a second shielding member for shielding X-rays from the X-ray source toward the first reflecting surface. A control member, wherein the controller uses the first shielding member to shield X-rays from the X-ray source toward the second reflecting surface, and uses the second shielding member to perform the first reflection from the X-ray source. You may switch between a 1st state and a 2nd state by selecting either among the states which shield the X-ray which goes to a surface. In this case, there is no need to move the first reflecting surface and the second reflecting surface.

  In this X-ray imaging apparatus, the imaging optical system may have a third reflecting surface that totally reflects X-rays from the sample and forms an image on the detector. In this case, it is not necessary to change the optical elements constituting the imaging optical system and the arrangement thereof according to the selection of X-ray energy.

  In the X-ray imaging apparatus, the third reflecting surface may totally reflect the X-rays in the total energy region that is totally reflected on the first reflecting surface and the second reflecting surface. In this case, X-rays in the energy region used for sample observation can be suppressed from being removed by the imaging optical system.

  The X-ray imaging apparatus includes a filter that is disposed on the reference line and removes X-rays on the low energy region side from among the X-rays in the energy region that are totally reflected on the first reflection surface and the second reflection surface. Also good. In this case, X-rays on the low energy region side that are not used for sample observation can be removed, so that the contrast of the obtained X-ray image can be improved.

  The X-ray imaging apparatus may include a third shielding member that is arranged on the reference line and shields the X-rays that enter the detector without passing through the condensing optical system. In this case, X-rays in an energy region not used for sample observation are suppressed from entering the detector, so that the contrast of the obtained X-ray image can be further improved.

  The X-ray imaging method according to the present invention is an X-ray imaging method using the above-described X-ray imaging apparatus, and the state of the condensing optical system is set to one of the first state and the second state by the control unit. A selection step for selecting the X-ray, an emission step for emitting X-rays irradiated to the sample from the X-ray source, a condensing step for condensing the X-ray emitted in the emission step on the sample by a condensing optical system, and imaging An imaging step of imaging an X-ray from the sample on the detector by the optical system, and a detection step of detecting the X-ray imaged in the imaging step by the detector.

  Since this X-ray imaging method uses the above-mentioned X-ray imaging apparatus, the sample can be easily observed while selecting an X-ray energy region.

  According to the X-ray imaging apparatus and the X-ray imaging method of the present invention, a sample can be easily observed while selecting an X-ray energy region.

It is a figure which shows the structure of the X-ray imaging device which concerns on 1st Embodiment. It is a figure which shows the structure of a condensing optical system and a control part. It is a figure explaining the dimension of an optical element. It is a figure explaining the relationship between the total reflection critical angle of X-rays, and the energy of X-rays. It is a figure which shows the structure of the X-ray imaging device which concerns on the modification of 1st Embodiment. It is a figure which shows the structure of the X-ray imaging device which concerns on 2nd Embodiment. It is a figure which shows the structure of the X-ray imaging device which concerns on 3rd Embodiment. It is a figure which shows the structure of the X-ray imaging device which concerns on a comparative example. It is a figure which shows the relationship between the energy of a X-ray, the transmittance | permeability, and a reflectance. It is a figure which shows the relationship between the energy of a X-ray, the transmittance | permeability, and a reflectance.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

(First embodiment)
With reference to FIG.1 and FIG.2, the X-ray imaging device which concerns on 1st Embodiment is demonstrated. FIG. 1 is a diagram illustrating a configuration of the X-ray imaging apparatus according to the first embodiment. More specifically, FIG. 1A shows a case where the state of the condensing optical system is the first state, and FIG. 1B shows a state where the state of the condensing optical system is the second state. It is a figure which shows a case. FIG. 2 is a diagram for explaining dimensions of the optical element.

  As shown in FIG. 1, the X-ray imaging apparatus 10A includes an X-ray source 1, a filter 2, a condensing optical system 3A, a shielding member (third shielding member) 4, and a shielding member (third shielding member). ) 5, an imaging optical system 6, a detector 7, and a control unit 8 (see FIG. 3). The X-ray imaging apparatus 10A is, for example, a soft X-ray 3D microscope. The sample S is separated by a distance L0 from the X-ray source 1 and a distance L3 from the detector 7 on the reference line A from the X-ray source 1 to the detector 7, and is held by a sample holder (not shown). Yes.

  The X-ray absorption coefficient varies depending on the energy of X-rays even for the same substance. Therefore, in the X-ray imaging apparatus 10A, the X-ray energy used for observation is selected according to the constituent material of the sample S. For example, X-rays in an energy region of 1 keV to several keV are used for observation of a material having a low atomic number (Z) (light element material). For observation of a biological sample containing water, X-rays in the energy region of 285 eV to 543 eV called “water window” are used. In the X-ray imaging apparatus 10A, the internal structure of the light element material and the biological sample can be observed by using X-rays in such an energy region. By rotating the sample S, the sample S can also be observed three-dimensionally. The rotation axis B of the sample S is, for example, perpendicular to the reference line A. When the energy of X-rays used is low (˜5 keV), the X-ray imaging apparatus 10A may be installed in a vacuum container (not shown) in order to avoid the attenuation of X-rays by air.

  The X-ray source 1 emits X-rays 20 that irradiate the sample S. The X-ray source 1 is, for example, an electron beam excitation type (electron beam impact type) X-ray source, a plasma X-ray source using a laser and gas discharge, or the like. The X-ray source 1 is an X-ray in an energy region (285 eV to 543 eV) used for observation of a biological sample as described above, an X-ray in an energy region (1 keV to several keV) used for observation of a light element material, or the like. Is emitted. When an electron beam excitation X-ray source is used as the X-ray source 1, the emitted X-ray 20 is composed of characteristic X-rays and bremsstrahlung X-rays. Characteristic X-rays are high in intensity, and energy is determined by the material constituting the target. The bremsstrahlung X-ray has a low intensity, and the energy is determined by the acceleration voltage. Characteristic X-rays are used for observation. As a target having characteristic X-rays in the energy region as described above, for example, an oxide target, a Ti target, or the like is used.

  The filter 2 is disposed on the reference line A. The filter 2 is, for example, a metal filter such as Be or Ti. The filter 2 passes X-rays 20 in the energy region of energy E0 or higher and removes X-rays 20 in the energy region lower than energy E0. That is, the filter 2 restricts the X-rays 20 emitted from the X-ray source 1 to the X-rays 20 having energy E0 or more and emits them to the condensing optical system 3A. The threshold value energy E0 is determined by the material and thickness of the filter 2. Therefore, the material and thickness of the filter 2 are determined according to the energy of the X-ray 20 used for observation. A plurality of types of filters 2 are prepared, and can be replaced relatively easily by arranging and retracting them on the optical path of the X-ray 20 by a moving mechanism (not shown).

  The condensing optical system 3 </ b> A collects the X-ray 20 emitted from the X-ray source 1 and passing through the filter 2 on the sample S. The condensing optical system 3A has an optical element 30A. The optical element 30A is, for example, an aspherical mirror. The optical element 30A is, for example, a cylindrical oblique incidence reflecting mirror, and is arranged on the reference line A so that the central axis coincides with the reference line A. The optical element 30A collects light by reflecting the X-rays 20 on its inner surface. The optical element 30A is a reflection optical system using total reflection, and is, for example, a Walter mirror, a rotation ellipsoid mirror, a rotation paraboloid mirror, or the like including a spheroid and a hyperbola. Here, the optical element 30 </ b> A includes a first optical element 31, a second optical element 32, and a connecting pipe 33.

  The first optical element 31 is a cylindrical oblique incidence reflecting mirror, and is disposed on the reference line A so that the central axis coincides with the reference line A. The first optical element 31 is, for example, a spheroid mirror. The first optical element 31 includes an end 31a, an end 31b, and a first reflecting surface 31c for condensing the X-ray 20 emitted from the X-ray source 1 on the sample S by total reflection. . The end 31a is disposed on the X-ray source 1 side, and the end 31b is disposed on the detector 7 side. The end portion 31a is disposed at a distance L1 from the X-ray source 1 along the reference line A.

  The first reflecting surface 31c is a curved surface that forms the inner surface of the first optical element 31, and connects the end 31a and the end 31b. The first reflecting surface 31c is a surface that is disposed on the reference line A and is used to collect the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. The first reflecting surface 31 c is line symmetric with respect to the reference line A. That is, the first optical element 31 focuses the light by reflecting the X-rays 20 by the first reflecting surface 31c. The first reflecting surface 31c is inclined with respect to the reference line A at a first inclination angle α1.

  The second optical element 32 is integrated with the first optical element 31 in a state of being aligned with the first optical element 31 along the reference line A. The second optical element 32 is a cylindrical oblique incidence reflecting mirror, and is disposed on the reference line A so that the central axis coincides with the reference line A. The second optical element 32 is, for example, a spheroid mirror. The second optical element 32 includes an end portion 32a, an end portion 32b, and a second reflection surface 32c for condensing the X-ray 20 emitted from the X-ray source 1 on the sample S by total reflection. . The end portion 32a is disposed on the X-ray source 1 side, and the end portion 32b is disposed on the detector 7 side. The end 32a is disposed at a distance L2 from the X-ray source 1 along the reference line A.

  The second reflecting surface 32c is a curved surface forming the inner surface of the second optical element 32, and connects the end portion 32a and the end portion 32b. The second reflection surface 32c is a surface that is disposed on the reference line A and is used to collect the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. The second reflecting surface 32 c is line symmetric with respect to the reference line A. That is, the second optical element 32 collects light by reflecting the X-rays 20 by the second reflecting surface 32c. The second reflecting surface 32c is inclined with respect to the reference line A at the second inclination angle α2. The second inclination angle α2 and the first inclination angle α1 are different. Since the first optical element 31 is disposed closer to the X-ray source 1 than the second optical element 32 and has a larger inner diameter as will be described later, the second inclination angle α2 is larger than the first inclination angle α1.

  The connecting pipe 33 is a tubular member that connects the first optical element 31 and the second optical element 32, and is arranged so that the central axis coincides with the reference line A. The connection pipe 33 includes an end portion 33a and an end portion 33b. The end portion 33a is disposed on the first optical element 31 side and is connected to the end portion 31b. The end portion 33b is disposed on the second optical element 32 side and is connected to the end portion 32a. The inner surface of the connecting tube 33 may be coated with a substance that does not reflect the X-rays 20 and absorbs the X-rays 20. Thereby, the X-rays reflected by the inner surface of the connection tube 33 are suppressed from entering the imaging optical system 6.

  Here, as shown in FIG. 2A, the dimensions of the first optical element 31 are the length L6 along the reference line A (see FIG. 1), the inner diameter D1 of the end 31a, and the inner diameter of the end 31b. D2. The inner diameter D1 is larger than the inner diameter D2. The dimensions of the second optical element 32 are a length L8 along the reference line A, an inner diameter D3 of the end portion 32a, and an inner diameter D4 of the end portion 32b. The inner diameter D3 is smaller than the inner diameter D2 and larger than the inner diameter D4. The dimensions of the connecting pipe 33 are a length L7 along the reference line A, an inner diameter D2 of the end portion 33a, and an inner diameter D3 of the end portion 33b.

  Returning to FIG. 1, the description will be continued. The condensing optical system 3A takes a first state shown in FIG. 1A and a second state shown in FIG. 1B depending on the position of the optical element 30A. The values of the distance L1 and the distance L2 are different between the first state and the second state. The distance L1 in the first state (hereinafter referred to as distance L1 (S1)) is longer than the distance L1 in the second state (hereinafter referred to as distance L1 (S2)). The distance L2 (S1) in the first state is longer than the distance L2 (S2) in the second state.

  In the first state, the first reflecting surface 31 c is used to collect the X-ray 20. That is, in the first state, the X-ray 20 is incident on the first reflecting surface 31c at the first oblique incident angle β1, and the X-ray 20 totally reflected by the first reflecting surface 31c is collected on the sample S. The first oblique incident angle β1 is defined as an angle formed by the optical axis C3 of the X-ray 20 incident on the center position in the direction along the reference line A of the first reflecting surface 31c and the first reflecting surface 31c.

  In the second state, the second reflecting surface 32 c is used to collect the X-ray 20. That is, in the second state, the X-ray 20 is incident on the second reflecting surface 32c at the second oblique incident angle β2, and the X-ray 20 totally reflected by the second reflecting surface 32c is collected on the sample S. The second oblique incident angle β2 is defined as an angle formed by the optical axis C4 of the X-ray 20 incident on the center position in the direction along the reference line A of the second reflecting surface 32c and the second reflecting surface 32c.

  The condensing optical system 3A sets the length L7 of the connecting tube 33, so that the arrangement of the first reflecting surface 31c and the second reflecting surface 32c is reflected by the second reflecting surface 32c in the first state. The line 20 does not enter the imaging optical system 6, and in the second state, the X-ray 20 reflected by the first reflecting surface 31 c is set not to enter the imaging optical system 6. The condensing optical system 3A includes a shielding member 4 and a shielding member 5 to be described later, so that in the first state, the X-ray 20 reflected by the second reflecting surface 32c does not enter the imaging optical system 6, and In the two states, the X-ray 20 reflected by the first reflecting surface 31c may be set so as not to enter the imaging optical system 6.

  The optical axis C1 of the X-ray 20 (hereinafter referred to as first incident light) totally reflected by the first reflecting surface 31c in the first state and the reference line A form an angle γ. The optical axis C1 is defined as the optical axis of the X-ray 20 emitted to the sample S from the center position in the direction along the reference line A of the first reflecting surface 31c. The optical axis C2 of the X-ray 20 (hereinafter referred to as second incident light) totally reflected by the second reflecting surface 32c in the second state and the reference line A form an angle γ. The optical axis C2 is defined as the optical axis of the X-ray 20 emitted to the sample S from the center position in the direction along the reference line A of the second reflecting surface 32c.

  Thus, the angle formed between the optical axis C1 of the first incident light and the reference line A and the angle formed between the optical axis C2 of the second incident light and the reference line A are both angles γ and are equivalent to each other. It is. That is, the first incident light and the second incident light have a common optical path. More specifically, the optical path of the first incident light and the optical path of the second incident light have overlapping portions. In other words, the numerical apertures of the first optical element 31 and the second optical element 32 are both equal to the numerical aperture of the imaging optical system 6. Further, as described above, the first inclination angle α1 and the second inclination angle α2 are different from each other. From the geometric relationship between the angle γ, the first inclination angle α1, and the first oblique incidence angle β1, and the geometric relationship between the angle γ, the second inclination angle α2, and the second oblique incidence angle β2, the first oblique incidence is performed. The angle β1 and the second oblique incident angle β2 are different from each other. A configuration for switching the first state and the second state of the condensing optical system 3A will be described later with reference to FIG.

  The shielding member 4 and the shielding member 5 are arranged on the reference line A. The shielding member 4 and the shielding member 5 have a circular shape when viewed from the direction along the reference line A. The outer diameter of the shielding member 4 is smaller than the inner diameter D4 (see FIG. 2A). The outer diameter of the shielding member 5 is smaller than an inner diameter D5 (see FIG. 2B) described later. The shielding member 4 is arranged on the X-ray source 1 side with respect to the sample S on the reference line A. The shielding member 5 is arranged on the detector 7 side with respect to the sample S on the reference line A.

  The shielding member 4 is arranged inside the optical path of the first incident light and the optical path of the second incident light (on the reference line A side), and shields the X-ray 20 incident on the detector 7 without passing through the condensing optical system 3A. To do. The shielding member 5 is disposed on the inner side (reference line A side) of the X-ray 20 incident on the reflecting surface 61c from the sample S, and enters the detector 7 without passing through the condensing optical system 3A. Shield. According to the shielding member 4 and the shielding member 5, X-rays 20 that do not contribute to imaging such as scattered X-rays from the surroundings can be removed.

  The imaging optical system 6 is arranged on the reference line A, expands the X-ray 20 from the sample S, and forms an image on the detector 7. The imaging optical system 6 has a third optical element 60. The third optical element 60 is, for example, an aspherical mirror. The third optical element 60 is, for example, a cylindrical oblique incidence reflector, and is arranged on the reference line A so that the central axis coincides with the reference line A. The third optical element 60 collects light by reflecting the X-rays 20 on its inner surface. The third optical element 60 is a reflection optical system using total reflection, and is, for example, a Walter mirror including a spheroid and a hyperboloid.

  The third optical element 60 includes a first portion 61 and a second portion 62. The first portion 61 includes an end portion 61a, an end portion 61b, and a reflective surface (third reflective surface) 61c. The end portion 61a is disposed on the sample S side, and the end portion 61b is disposed on the detector 7 side. The end portion 61a is disposed at a distance L4 from the sample S along the reference line A. The reflecting surface 61c of the first portion 61 corresponds to, for example, a rotating hyperboloid of a Walter mirror, and is inclined with respect to the reference line A at a third inclination angle α3. The reflecting surface 61c is line symmetric with respect to the reference line A. The third inclination angle α3 is larger than the second inclination angle α2 and the first inclination angle α1.

  The second part includes an end 62a, an end 62b, and a reflective surface 62c. The end 62a is disposed on the sample S side, and the end 62b is disposed on the detector 7 side. The end 62a is disposed at a distance L5 from the X-ray source 1 along the reference line A. The reflecting surface 62c of the second portion 62 corresponds to, for example, a spheroidal surface of a Walter mirror. The reflecting surface 62c is line symmetric with respect to the reference line A. The end portion 61b and the end portion 62a are connected to each other.

  Here, as shown in FIG. 2B, the dimensions of the first portion 61 of the third optical element 60 are a length L9 along the reference line A (see FIG. 1), an inner diameter D5 of the end 61a, and This is the inner diameter D6 of the end 61b. The dimensions of the second portion 62 of the third optical element 60 are the length L10 along the reference line A, the inner diameter D6 of the end portion 62a, and the inner diameter D7 of the end portion 62b.

  Returning to FIG. 1, the description will be continued. The detector 7 detects the X-ray 20 from the sample S. The detector 7 has a light receiving surface, and after passing through the sample S, detects the X-rays 20 imaged on the light receiving surface by the imaging optical system 6. The detector 7 includes, for example, an X-ray detection element such as a CCD element. Three-dimensional observation of the sample S is also possible by rotating the sample S and photographing it with the detector 7 and performing image reconstruction.

  FIG. 3 is a diagram illustrating the configuration of the condensing optical system and the control unit. As shown in FIG. 3, the condensing optical system 3 </ b> A further includes a stage 11, a holder 12, and a drive motor 13. The holder 12 holds the optical element 30 </ b> A on the outer peripheral surface of the connection pipe 33 on the stage 11. The holder 12 is disposed on the stage 11 so as to be movable along the reference line A. The drive motor 13 is a pulse motor, for example, and moves the holder 12 on the stage 11 along the reference line A.

  The control unit 8 is electrically connected to the drive motor 13. The control unit 8 is configured by a computer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The control unit 8 sends a control signal to the drive motor 13 to drive the drive motor 13. The control unit 8 switches between the first state and the second state by moving the first optical element 31 and the second optical element 32 along the reference line A (for example, in parallel). That is, the control unit 8 changes the state of the condensing optical system 3A between the first state where the X-rays 20 totally reflected by the first reflecting surface 31c are condensed on the sample S and the total reflection by the second reflecting surface 32c. Control is performed to switch between the second state in which the X-ray 20 is condensed on the sample S.

  Next, an X-ray imaging method using the X-ray imaging apparatus configured as described above will be described. In the X-ray imaging method according to the present embodiment, first, the state of the condensing optical system 3A is selected from the first state and the second state (selection step). Thereby, the energy region of the X-ray 20 removed by the condensing optical system 3A can be selected for the following reason.

FIG. 4A is a diagram for explaining the oblique incident angle of X-rays, and FIG. 4B is a graph showing the relationship between X-ray energy and reflectance. As shown in FIG. 4A, when X-rays enter a certain material plane, total reflection occurs when an oblique incident angle θ, which is an angle formed by the plane and the X-rays, is equal to or less than a predetermined value. The maximum angle at which this total reflection occurs is called the total reflection critical angle θc. The magnitude of the total reflection critical angle θc is determined by the material of the reflection plane and the X-ray energy. Using the density ρ (g / cm ³ ) and the X-ray wavelength λ (nm) of the material of the reflection plane, the formula (1) Indicated by
θc (°) = 94.2 × 10 ⁻¹ × λ × (ρ) ^1/2 (1)

Further, the relationship between the X-ray energy E and the X-ray wavelength λ is expressed by Expression (2).
E (eV) = 1240 / λ (2)

  As shown in FIG. 4B, when the oblique incident angle is θa, the reflectivity is drastically decreased when the X-ray energy is Ea, and when the oblique incident angle is θb (θa> θb), the X-ray energy is With Eb, the reflectivity rapidly decreases. That is, if the oblique incident angle is set to θa, X-rays having an X-ray energy of Ea or more are removed, and if the oblique incident angle is set to θb, X-rays having an X-ray energy of Eb or more are removed. Recognize. In this way, by selecting the oblique incident angle, it is possible to select an X-ray energy region that is removed without being reflected.

  When the first state is selected in the selection step, the control unit 8 does not switch the state of the condensing optical system 3A if the state of the condensing optical system 3A is the first state in advance. Further, if the condensing optical system 3A is in the second state, the control unit 8 drives the drive motor 13 to move the first optical element 31 and the second optical element 32 along the reference line A (for example, Move in parallel). Thereby, the state of the condensing optical system 3A is switched to the first state. On the other hand, when the second state is selected in the selection step, similarly, the control unit 8 does not switch the state of the condensing optical system 3A if the state of the condensing optical system 3A is the second state in advance. Further, if the state of the condensing optical system 3A is the first state, the controller 8 drives the drive motor 13 to move the first optical element 31 and the second optical element 32 in parallel with the reference line A. . Thereby, the state of the condensing optical system 3A is switched to the second state.

  Subsequently, X-rays 20 irradiating the sample S are emitted from the X-ray source 1 (extraction step). X-rays 20 emitted from the X-ray source 1 enter the filter 2. Of the X-rays 20 incident on the filter 2, the X-rays 20 on the low energy region side lower than the energy E0 are removed, and the X-rays 20 in the energy region equal to or higher than the energy E0 are emitted from the filter 2.

  Subsequently, the X-ray 20 transmitted through the filter 2 is condensed on the sample S by the condensing optical system 3A (condensing step). In the case of the first state, the X-rays 20 that have passed through the filter 2 are totally reflected by the first reflecting surface 31c and collected on the sample S. At this time, the X-ray 20 having an energy equal to or greater than the energy E1 having the first oblique incident angle β1 as the total reflection critical angle is hardly reflected by the first reflecting surface 31c (reflectance of 30% or less). Therefore, the X-ray 20 having energy equal to or higher than E1 is removed by the condensing optical system 3A, and the other X-rays 20 are condensed on the sample S.

  On the other hand, in the second state, the X-rays 20 that have passed through the filter 2 are totally reflected by the second reflecting surface 32c and collected on the sample S. At this time, X-rays 20 having energy equal to or greater than energy E2 having the second oblique incident angle β2 as the total reflection critical angle are hardly reflected by the second reflecting surface 32c (reflectance of 30% or less). Therefore, the X-ray 20 having energy equal to or higher than E2 is removed by the condensing optical system 3A, and the other X-rays 20 are condensed on the sample S.

  That is, here, the X-ray 20 on the low energy side is removed by the filter 2, and the X-ray 20 on the high energy side is removed by the condensing optical system 3A. Thereby, the X-rays 20 in a predetermined range (E0 to E1 in the first state, E0 to E2 in the second state) between the low energy side and the high energy side are selected. As can be derived from the above equations (1) and (2), the energy E2 is higher than the energy E1 (E2> E1). In both cases of the first state and the second state, the X-rays 20 that pass through the filter 2 and go to the sample S without passing through the condensing optical system 3A are shielded by the shielding member 4.

  Subsequently, the X-ray 20 from the sample S is imaged by the imaging optical system 6 (imaging step). In the imaging optical system 6, the X-ray 20 is reflected twice by each of the reflecting surface 61c and the reflecting surface 62c. As described above, since the first incident light and the second incident light have the same optical path, the optical path of the X-ray 20 from the sample S is also common in the first state and the second state. Accordingly, in both the first state and the second state, in the imaging optical system 6, the X-ray 20 from the sample S enters the reflecting surface 61c at the third oblique incident angle β3. For this reason, it is not necessary to move the positions of the sample S, the imaging optical system 6 and the detector 7 in either case of the first state or the second state. Further, since the imaging optical system 6 and the detector 7 are not moved, the magnification does not change. The third oblique incident angle β3 is defined as an angle formed by the reflection surface 61c and the optical axis C5 of the X-ray 20 incident on the center position in the direction along the reference line A of the reflection surface 61c. Here, the reflecting surface 62c is set so that the X-rays 20 from the reflecting surface 61c are incident at an oblique incident angle equal to the third oblique incident angle β3.

  Here, as described above, the third inclination angle α3 is larger than the second inclination angle α2 and the first inclination angle α1. From the geometrical relationship with the third oblique incident angle β3 and the like, the third oblique incident angle β3 is smaller than the first oblique incident angle β1 and the second oblique incident angle β2. Therefore, the energy E3 having the third oblique incident angle β3 as the total reflection critical angle is higher than the energy E1 and the energy E2 (E3> E1, E2). That is, the reflection surface 61c causes the detector 7 to form an image by totally reflecting the X-rays 20 in the total energy region totally reflected by the first reflection surface 31c and the second reflection surface 32c. X-rays 20 from the sample S toward the detector 7 without passing through the imaging optical system 6 are shielded by the shielding member 5.

  Finally, the X-ray 20 imaged in the imaging step is detected by the detector 7 (detection step). In the case of the first state, in the detection step, an image captured by the X-ray 20 having energy of E0 to E1 is obtained. In the case of the second state, the detector 7 obtains an image captured by the X-ray 20 having energy of E0 to E2.

  FIG. 5 is a diagram illustrating a configuration of an X-ray imaging apparatus according to a modification of the first embodiment. As shown in FIGS. 1 and 5, the X-ray imaging apparatus 10 </ b> A includes the condensing optical system 3 </ b> A, whereas the X-ray imaging apparatus 10 </ b> B according to the modified example includes a condensing optical system 3 </ b> B. ing. The condensing optical system 3A includes an optical element 30A, whereas the condensing optical system 3B is different in that it includes an optical element 30B. Further, the optical element 30 </ b> A has a connecting pipe 33, whereas the optical element 30 </ b> B is different in that it has a connecting pipe 34.

  The connecting pipe 34 is different from the connecting pipe 33 in terms of shape. The connecting pipe 34 includes a parallel portion 35 parallel to the reference line A and an intersecting portion 36 that intersects the reference line A. Thus, since the connection pipe 34 includes the parallel part 35, it is easy to hold it by the holder 12 (see FIG. 3).

(Second Embodiment)
FIG. 6 is a diagram illustrating a configuration of the X-ray imaging apparatus according to the second embodiment. As shown in FIGS. 1 and 6, the X-ray imaging apparatus 10A according to the first embodiment includes a condensing optical system 3A, whereas the X-ray imaging apparatus 10C according to the second embodiment includes condensing optics. The difference is that the system 3C is provided.

  The condensing optical system 3C includes a first optical element 31 including a first reflecting surface 31c, and a second optical element 32 including a second reflecting surface 32c and configured separately from the first optical element 31. ing. That is, the condensing optical system 3A includes the first optical element 31 and the second optical element 32 as one integrated optical element 30A, whereas the condensing optical system 3C is separated as a separate body. This is different from the condensing optical system 3A in that the first optical element 31 and the second optical element 32 configured as described above are provided.

  The first optical element 31 and the second optical element 32 are provided so as to be movable in a direction intersecting the reference line A by a moving mechanism (not shown) such as a stage. Here, the first optical element 31 and the second optical element 32 are provided to be movable in a direction orthogonal to the reference line A. The control unit 8 sends a control signal to the moving mechanism, and arranges the first reflecting surface 31c at a position for condensing the X-ray 20 emitted from the X-ray source 1 on the sample S by total reflection. Thereby, the state of the condensing optical system 3C becomes the first state. In addition, the control unit 8 retracts the second reflecting surface 32c from the condensing position. For example, the control unit 8 retracts the second reflecting surface 32 c to a place isolated from the X-ray source 1.

  In addition, the control unit 8 retracts the first reflecting surface 31c from the position for condensing the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. Thereby, the state of the condensing optical system 3 </ b> C becomes the second state. For example, the control unit 8 retracts the first reflecting surface 31 c to a place isolated from the X-ray source 1. Further, the control unit 8 arranges the second reflecting surface 32c at a position for condensing the X-ray 20 emitted from the X-ray source 1 on the sample S by total reflection. As described above, in the X-ray imaging apparatus 10 </ b> C, the control unit 8 switches between the first state and the second state by moving one of the first optical element 31 and the second optical element 32.

(Third embodiment)
FIG. 7 is a diagram illustrating a configuration of an X-ray imaging apparatus according to the third embodiment. As shown in FIGS. 6 and 7, the X-ray imaging apparatus 10C according to the second embodiment includes the condensing optical system 3C, whereas the X-ray imaging apparatus 10D according to the third embodiment includes the condensing optics. The difference is that a system 3D is provided. The X-ray imaging apparatus 10D is different from the X-ray imaging apparatus 10C in that it further includes a shielding member 15 and a shielding member 16.

  In the condensing optical system 3D, the first optical element 31 is fixedly held at a position where the first reflecting surface 31c collects the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. . The second optical element 32 is fixed and held at a position where the second reflecting surface 32c collects the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. The X-ray imaging apparatus 10D matches the X-ray imaging apparatus 10C in other points.

  The shielding member 15 is used to shield the X-ray 20 from the X-ray source 1 toward the second reflecting surface 32c. The shielding member 15 has a circular shape when viewed from the direction along the reference line A. The control unit 8 is on the optical path of the X-ray 20 from the X-ray source 1 toward the second reflecting surface 32c and inside the optical path of the X-ray 20 from the X-ray source 1 toward the first reflecting surface 31c (reference line A The shielding member 15 is disposed on the side. Thereby, the shielding member 15 shields the X-rays 20 from the X-ray source 1 toward the second reflecting surface 32c while allowing the X-rays 20 from the X-ray source 1 toward the first reflecting surface 31c to pass therethrough. That is, the condensing optical system 3D is in the first state.

  The shielding member 16 is used to shield the X-ray 20 from the X-ray source 1 toward the first reflecting surface 31c. The shielding member 16 has an annular shape when viewed from the direction along the reference line A. The control unit 8 is on the optical path of the X-ray 20 from the X-ray source 1 toward the first reflecting surface 31c, and the inner edge of the shielding member 16 is the optical path of the X-ray 20 from the X-ray source 1 toward the second reflecting surface 32c. The shielding member 16 is arranged so as to be located outside the front side. Thereby, the shielding member 16 shields the X-rays 20 from the X-ray source 1 toward the first reflection surface 31c while allowing the X-rays 20 from the X-ray source 1 toward the second reflection surface 32c to pass therethrough. That is, the condensing optical system 3D is in the second state.

  As described above, the control unit 8 uses the shielding member 15 to shield the X-ray 20 from the X-ray source 1 toward the second reflecting surface 32 c, and uses the shielding member 16 to perform the first reflection from the X-ray source 1. The first state and the second state are switched by selecting one of the states that shield the X-rays 20 toward the surface 31c.

  As described above, the X-ray imaging apparatuses 10A to 10D according to the present embodiment include the control unit 8 that switches the states of the condensing optical systems 3A to 3D. The control unit 8 performs a first state in which the X-ray 20 is totally reflected by the first reflecting surface 31c and enters the sample S, and a second state in which the X-ray 20 is totally reflected by the second reflecting surface 32c and enters the sample S. Switch between states. The first inclination angle α1 of the first reflection surface 31c and the second inclination angle α2 of the second reflection surface 32c are different from each other. In addition, the angle formed between the optical axis C1 of the first incident light and the reference line A and the angle formed between the optical axis C2 of the second incident light and the reference line A are both angles γ and are equivalent to each other. . Therefore, the first oblique incident angle β1 of the X-ray 20 to the first reflecting surface 31c in the first state and the second oblique incident angle β2 of the X-ray 20 to the second reflecting surface 32c in the second state are mutually different. Different.

  As described with reference to FIG. 4, when the oblique incident angle θ of X-rays to the reflecting surface is different, the energy region of X-rays totally reflected by the reflecting surface is different. Thereby, by switching between the first state and the second state, the X-ray 20 used for observation of the sample S is totally reflected by the X-rays in the energy region totally reflected by the first reflecting surface 31c and the second reflecting surface 32c. It can be selected from X-rays in the energy region to be reflected.

  As described above, the angle formed between the optical axis C1 of the first incident light and the reference line A and the angle formed between the optical axis C2 of the second incident light and the reference line A are both angles γ. It is equivalent. For this reason, the incident state of the X-rays 20 to the imaging optical system 6 does not change between the first state and the second state. Therefore, it is not necessary to align the imaging optical system 6 and the detector 7 in accordance with the selection of the energy of the X-ray 20. As described above, in the X-ray imaging apparatuses 10A to 10D, the sample S can be easily observed while selecting the energy region of the X-ray 20.

  The condensing optical systems 3 </ b> A to 3 </ b> D are configured to select the energy region of the X-rays 20 to be removed using total reflection, and thus have the selective reflection characteristics of the multilayer mirror as described in Patent Document 2. The use efficiency of the X-ray 20 can be improved as compared with the configuration to be used. For example, the reflectance of the “water window” region of the multilayer mirror is several tens of percent, and the utilization efficiency is low. Further, the utilization efficiency is further lowered in the energy region beyond that.

  FIG. 8 is a diagram illustrating a configuration of an X-ray imaging apparatus according to a comparative example. As shown in FIGS. 1 and 8, the X-ray imaging apparatus 100 according to the comparative example is different from the X-ray imaging apparatus 10A according to the first embodiment in that an optical element 103 is provided as a condensing optical system. . The optical element 103 is a spheroid mirror. When the X-ray imaging apparatus 100 changes the target substance to change the energy of the X-ray 20 used for observing the sample S, the X-ray imaging apparatus 100 not only replaces the filter 2 but also replaces the optical element 103. It is necessary to change the material and the oblique incident angle. The replacement work of the optical element 103 requires highly accurate position adjustment, and takes time.

  Further, when the oblique incident angles of the optical element 103 and the third optical element 60 are changed, it is necessary to allow the X-rays 20 collected by the optical element 103 to efficiently enter the third optical element 60. In other words, the numerical apertures of the optical element 103 and the third optical element 60 need to be equal. For this reason, the positions of the focal points of the optical element 103 and the third optical element 60 change, and accordingly, the positions of the X-ray source 1, the sample S, and the detector 7 may change. Therefore, the X-ray imaging apparatus 100 according to the comparative example cannot easily observe the sample S while selecting the energy region of the X-ray 20 as in the X-ray imaging apparatuses 10A to 10D according to the present embodiment. .

  In the X-ray imaging devices 10 </ b> A to 10 </ b> D, the imaging optical system 6 forms an image on the detector 7 by totally reflecting the X-rays 20 in the total energy region totally reflected by the first reflecting surface 31 c and the second reflecting surface 32 c. Let For this reason, it is possible to suppress the X-rays 20 in the energy region used for observing the sample S from being removed by the imaging optical system 6. Further, since the imaging optical system 6 forms an image by totally reflecting the X-ray 20, it is not necessary to change the third optical element 60 and its arrangement according to the selection of the energy of the X-ray 20. On the other hand, in an imaging optical system using a multilayer mirror, it is necessary to change the film thickness and material of the multilayer film for each X-ray energy. That is, in a system using a plurality of energy regions such as the X-ray imaging devices 10A to 10D, it is necessary to prepare a plurality of multilayer film mirrors by the number of energy regions to be used. Further, in the imaging optical system using the zone plate (ZP), the efficiency is lower than that of the imaging optical system 6 of the present embodiment, and the focal length changes depending on the energy of X-rays. Unlike optical elements such as multilayer mirrors and zone plates, a reflective optical system using total reflection is capable of producing multiple energies with one optical element under the condition that the oblique incident angle is smaller than the oblique incident angle of the condensing optical system. Can correspond to the area.

  Since the X-ray imaging devices 10 </ b> A to 10 </ b> D include the filter 2, the X-rays 20 on the low energy region side that are not used for observing the sample S can be removed. Thereby, the contrast of the obtained X-ray image can be improved. Furthermore, the X-ray imaging devices 10 </ b> A to 10 </ b> D include a shielding member 4 and a shielding member 5. For this reason, since the X-rays 20 in the energy region that are not used for the observation of the sample S are suppressed from entering the detector 7, the contrast of the obtained X-ray image can be further improved.

  In the X-ray imaging devices 10A and 10B, the first optical element 31 and the second optical element 32 are integrated. For this reason, the control unit 8 moves the first optical element 31 and the second optical element 32 by a common moving mechanism including the stage 11, the holder 12, the drive motor 13, and the like, thereby collecting the condensing optical system 3A, The state of 3B can be switched. For this reason, the structure of X-ray imaging device 10A, 10B can be simplified.

  In the X-ray imaging apparatus 10C, since the first optical element 31 and the second optical element 32 are configured separately, the first optical element 31 and the second optical element 32 can be moved, respectively. Therefore, the control unit 8 can easily arrange the first optical element 31 and the second optical element 32 at a position for condensing the X-ray 20 emitted from the X-ray source 1 on the sample S by total reflection. it can. Further, the control unit 8 can retract the unused first optical element 31 and second optical element 32 to a place isolated from the X-ray source 1. Therefore, there is no possibility that X-rays 20 totally reflected by the first optical element 31 and the second optical element 32 that are not used are incident on the imaging optical system 6. Further, since there is no connecting tube, there is no possibility that the X-rays 20 totally reflected by the connecting tube enter the imaging optical system 6.

  In the X-ray imaging apparatus 10 </ b> D, the control unit 8 switches between the first state and the second state by using one of the shielding member 15 and the shielding member 16. For this reason, it is not necessary to move the first optical element 31 and the second optical element 32. In addition, since the first optical element 31 and the second optical element 32 are configured separately and there is no connecting tube, the X-rays 20 totally reflected by the connecting tube are imaged optically as in the X-ray imaging apparatus 10C. There is no risk of entering the system 6.

  Further, since the X-ray imaging method according to the present embodiment uses the X-ray imaging apparatus 10A, the sample S can be easily observed while selecting the energy region of the X-ray 20. The same applies to the X-ray imaging devices 10B to 10D.

  The X-ray imaging apparatuses 10A to 10C and the X-ray imaging method according to the present embodiment have been described above, but the present invention is not limited to this. For example, if the distance L0 is sufficiently long and the optical element can be further installed, the condensing optical systems 3A to 3D have three or more reflecting surfaces and can select three or more X-ray energies. It is good. If it is not necessary to remove the X-rays 20 on the low energy region side, the filter 2 may not be provided. The position of the filter 2 is not limited to between the X-ray source 1 and the sample S, and may be between the sample S and the detector 7. The positions of the shielding member 4 and the shielding member 5 are anywhere on the reference line A as long as they are positions that shield the X-rays 20 incident on the detector 7 without passing through the condensing optical systems 3A to 3D. Good. Further, only one of the shielding member 4 and the shielding member 5 may be provided. Further, if the first inclination angle α1 and the second inclination angle α2 are larger than the third inclination angle α3, the first inclination angle α1 may be larger than the second inclination angle α2. Further, in the X-ray imaging apparatuses 10A and 10B, the shape of the connection pipe is not limited to the connection pipes 33 and 34, and is arbitrary.

  In the X-ray imaging apparatus 10C, the second optical element 32 is positioned on the optical path of the X-ray 20 totally reflected by the first reflecting surface 31c, and the X-ray 20 totally reflected by the first reflecting surface 31c is second optically reflected. In the case where it can be shielded by the element 32, the control unit 8 does not have to retract the second optical element 32 in the second state. Further, the place where the first reflecting surface 31c and the second reflecting surface 32c are retracted is not limited to the place isolated from the X-ray source 1, and the X-ray 20 emitted from the X-ray source 1 is applied to the sample S by total reflection. The position may not be a position for condensing light.

  In the X-ray imaging device 10D, the second optical element 32 is located on the optical path of the X-ray 20 totally reflected by the first reflecting surface 31c, and the X-ray 20 totally reflected by the first reflecting surface 31c is converted into the second optical element. When it can shield with the element 32, the control part 8 does not need to use the shielding member 16 in a 2nd state. Further, the first optical element 31 and the second optical element 32 may be integrated.

Example 1
As Example 1, a case where a light element material is observed will be described. As the X-ray imaging apparatus, an X-ray imaging apparatus corresponding to the X-ray imaging apparatus 10A according to the first embodiment is used. The condensing optical system is accurately adjusted at the time of installation, and a high-precision stage using a pulse motor is used to move the condensing optical system. Thereby, the positional accuracy when the 1st reflective surface and the 2nd reflective surface are rearranged is maintained.

  For observation, as an X-ray in an energy region having a large absorption coefficient for a light element of several keV or less, a characteristic X-ray L line (0.93 keV, 0.95 keV) when Cu (copper) is used as a target, and The characteristic X-ray M-line (around 1.78 keV) when W is used as the target is used.

  When Cu is used as the target and the acceleration voltage is 10 kV, the characteristic X-ray K-line (8.05 keV, 8.9 keV) and L-line (0.93 keV, 0.95 keV) and the bremsstrahlung X-ray of 10 keV or less Continuous X-rays are emitted. Here, the characteristic X-ray energy region (0.9 keV to 1 keV) of the characteristic X-ray is used as efficiently as possible, and other characteristic X-rays and continuous X-rays are removed. This suppresses a decrease in contrast due to a difference in X-ray absorption rate. Therefore, a Be foil having a thickness of 1 μm is used as a filter that has a transmittance of 80% or more at 0.9 keV to 1 keV and can remove X-rays of 400 eV or less.

Further, the material of the condensing optical system and the oblique incident angle are set so that the characteristic X-rays and continuous X-rays having high reflectivity at 0.9 keV to 1 keV and exceeding 1 keV can be removed as much as possible. Here, the first optical element is formed of SiO ₂ (ρ = 2.2 g / cm ³ ), and the first oblique incident angle β1 is 1.55 °. X-ray energy having a total reflection critical angle of 1.55 ° is 1.1 keV, and X-rays of 1.1 keV or higher are not reflected. Accordingly, it is possible to remove the characteristic X-ray K-rays of 8.05 keV and 8.9 keV and continuous X-rays of 1.1 keV or higher. As described above, observation in the X-ray energy region of 400 eV to 1.1 keV including the energy 0.93 keV and 0.95 keV of the L-ray of the characteristic X-ray becomes possible.

Next, a case where W is used as a target will be described. The Be foil having a thickness of 1 μm described above has a transmittance of 90% or more near 1.78 keV. Further, the second optical element is formed of SiO ₂ (ρ = 2.2 g / cm ³ ), and the second oblique incident angle β2 is set to 0.85 °. The X-ray energy having a total reflection critical angle of 0.85 ° is 1.9 keV, and X-rays of 1.9 keV or higher are not reflected. As described above, observation in the X-ray energy region of 400 eV to 1.9 keV including the vicinity of the energy 1.78 keV of the M-ray of the characteristic X-ray becomes possible.

As described above, the condensing optical system and the imaging optical system must satisfy the following conditions (1) to (3).
(1) The distances L0 in the first state and the second state are equal to each other.
(2) The angle formed between the optical axis C1 of the first incident light and the reference line A and the angle formed between the optical axis C2 of the second incident light and the reference line A are both angles γ and are equivalent to each other. (Ie, the numerical apertures of the first optical element and the second optical element are equivalent to the numerical aperture of the imaging optical system).
(3) The third oblique incident angle β3 is smaller than the second oblique incident angle β2.

  When the specifications of the condensing optical system and the imaging optical system are determined so as to satisfy these conditions, L0 = 337 mm, L1 (S1) = 170 mm, L2 (S1) = 317 mm, L1 (S2) = 155 mm, L2 (S2) = 302 mm, L3 = 3280 mm, L4 = 71 mm, L5 = 80 mm, L6 = 25 mm, L7 = 122 mm, L8 = 10 mm, L9 = 9 mm, L10 = 10.07 mm, D1 = 9.3 mm, D2 = 9.9. 2 mm, D3 = 1.86 mm, D4 = 1.6 mm, D5 = 4.06 mm, D6 = 4.53 mm, D7 = 4.57 mm, β1 = 1.55 °, β2 = 0.85 ° and β3 = 0. It will be 41 °.

  In addition, when the X-ray imaging apparatus corresponding to X-ray imaging apparatus 10C, 10D which concerns on 2nd Embodiment and 3rd Embodiment is used as an X-ray imaging apparatus, condensing optics so that the said conditions may be satisfied. When the specifications of the system and the imaging optical system are determined, L0 = 337 mm, L1 (S1) = 170 mm, L2 (S2) = 302 mm, L3 = 3280 mm, L4 = 71 mm, L5 = 80 mm, L6 = 25 mm, L8 = 10 mm, L9 = 9 mm, L10 = 10.07 mm, D1 = 9.3 mm, D2 = 9.2 mm, D3 = 1.86 mm, D4 = 1.6 mm, D5 = 4.06 mm, D6 = 4.53 mm, D7 = 4. 57 mm, β1 = 1.55 °, β2 = 0.85 °, and β3 = 0.41 °.

  FIG. 9 is a diagram showing the relationship between X-ray energy, transmittance, and reflectance. FIG. 9A shows the relationship between the X-ray energy and the transmittance of the filter (Be foil having a thickness of 1 μm), the X-ray energy and the first optical element of the condensing optical system (β1 = 1.55 °). ) And the second optical element (β2 = 0.85 °), and the relationship between the X-ray energy and the imaging optical system (β3 = 0.41 °). . Here, since the imaging optical system reflects X-rays twice on each of the two reflecting surfaces, it is indicated as “twice”. Note that the reflectivity is influenced by the absorption edges (543 eV, 1.8 keV) of oxygen and silicon contained in the materials of the condensing optical system and the imaging optical system, and thus the reflectivity shown in FIG. This graph is slightly different from the reflectance graph shown in FIG.

  FIG. 9B shows the transmission wavelength characteristics of the entire X-ray imaging apparatus in the first state and the second state and the difference between them. The transmission wavelength characteristic of the entire X-ray imaging apparatus in the first state is obtained by multiplying the transmittance of the filter, the reflectance of the first optical element, and the reflectance of the imaging optical system. The transmission wavelength characteristic of the entire X-ray imaging apparatus in the second state is obtained by multiplying the transmittance of the filter, the reflectance of the second optical element, and the reflectance of the imaging optical system.

  As shown in FIG. 9B, in the first state, X-rays in the energy region of 400 eV to 1.2 keV can be used for observation. In the second state, X-rays in the energy region of 400 eV to 1.8 keV can be used for observation. Therefore, in the first state, the characteristic X-ray M-line (around 1.78 keV) when W is used as a target can be used for observation. In the second state, the characteristic X-ray L line (0.93 keV, 0.95 keV) when Cu (copper) is used as the target can be used for observation. Thus, by switching between the first state and the second state, it is possible to see the difference in observation by X-rays in two different energy regions.

  In this example, X-ray images of two energy regions overlap on the low energy side. Therefore, as shown in FIG. 9B, according to the difference obtained by subtracting the transmission wavelength characteristic of the entire X-ray imaging apparatus in the first state from the transmission wavelength characteristic of the entire X-ray imaging apparatus in the second state. An X-ray image of an energy region of 1.0 keV to 1.8 keV is obtained. Actually, the first optical element and the second optical element have different visual field sizes and X-ray intensities focused on the sample. Therefore, an image obtained by simple subtraction between images is shown in FIG. It is a little different from the difference image shown in b).

(Example 2)
As Example 2, a case where a biological sample is observed will be described. As the X-ray imaging apparatus, an X-ray imaging apparatus corresponding to the X-ray imaging apparatus 10A according to the first embodiment is used. Biological samples are often observed using X-rays in the “water window” region (285 eV to 543 eV). In the “water window” region, the absorption of X-rays by water decreases, and the absorption by biological materials such as proteins and nucleic acids increases. For this reason, the image of the biological sample containing water is obtained with high contrast. It is desirable to remove X-rays of energy other than the “water window” region as much as possible in order to reduce the contrast of the image.

  When Ti (titanium) is used as a target and the acceleration voltage is 10 kV, characteristic X-ray L lines (0.45 keV, 0.46 keV) are emitted in the “water window” region. In addition, K-rays (4.51 keV, 4.93 keV) and bremsstrahlung X-rays of 10 keV or less are emitted. A Ti foil having a thickness of 0.05 μm is used as a filter having high transmittance at several hundreds eV and capable of removing X-rays of less than 10 eV.

  When the specifications of the condensing optical system and the imaging optical system are determined so as to satisfy the conditions (1) to (3), L0 = 266 mm, L1 (S1) = 136 mm, L2 (S1) = 259 mm, L1 (S2) = 128 mm, L2 (S2) = 251 mm, L3 = 3030 mm, L4 = 20 mm, L5 = 30 mm, L6 = 10 mm, L7 = 113 mm, L8 = 10 mm, L9 = 10 mm, L10 = 14.89 mm, D1 = 25 .13 mm, D2 = 25.02 mm, D3 = 1.86 mm, D4 = 1.6 mm, D5 = 4.19 mm, D6 = 5.62 mm, D7 = 6.25 mm, β1 = 5.4 °, β2 = 2. 65 ° and β3 = 1.35 °.

  In addition, when the X-ray imaging apparatus corresponding to X-ray imaging apparatus 10C, 10D which concerns on 2nd Embodiment and 3rd Embodiment is used as an X-ray imaging apparatus, condensing optics so that the said conditions may be satisfied. When the specifications of the system and the imaging optical system are determined, L0 = 266 mm, L1 (S1) = 136 mm, L2 (S2) = 251 mm, L3 = 3030 mm, L4 = 20 mm, L5 = 30 mm, L6 = 10 mm, L8 = 10 mm, L9 = 10 mm, L10 = 14.89 mm, D1 = 25.13 mm, D2 = 25.02 mm, D3 = 2.63 mm, D4 = 2.17 mm, D5 = 4.19 mm, D6 = 5.62 mm, D7 = 6.6. 25mm, β1 = 5.4 °, β2 = 2.65 ° and β3 = 1.35 °.

  The first oblique incident angle β1 is 5.4 °, and the X-ray energy having a total reflection critical angle of 5.4 ° is 287 eV. This is close to the low energy edge of the “water window” region. On the other hand, the second oblique incident angle β2 is 2.65 °, and the X-ray energy having a total reflection critical angle of 2.65 ° is 530 eV. This is close to the high energy edge of the “water window” region.

  FIG. 10 is a diagram illustrating the relationship between X-ray energy, transmittance, and reflectance. FIG. 10A shows the relationship between the X-ray energy and the transmittance of the filter (Ti foil having a thickness of 0.05 μm), the X-ray energy and the first optical element (β1 = 5. 4 °) and the reflectance of the second optical element (β2 = 2.65 °), and the relationship between the X-ray energy and the reflectance of the imaging optical system (β3 = 1.35 °). ing. FIG. 10B shows transmission wavelength characteristics of the entire X-ray imaging apparatus in the first state and the second state and the difference between them.

  As shown in FIG. 10A, the characteristic X-ray K line (4.51 keV, 4.93 keV) can be substantially removed. According to the second state, it can be observed with the characteristic X-ray L line (0.45 keV, 0.46 keV) which is the “water window” region. As shown in FIG. 10B, according to the difference in transmission wavelength characteristics of the entire X-ray imaging apparatus in the first state and the second state, energy components of 284 eV or less other than the “water window” region are reduced. The contrast of the X-ray image is improved.

  When observing a dry and relatively thick biological sample that does not contain water, the target may be a substance composed of C (carbon) such as graphite and DLC, and observed with carbon K-rays (282 eV). it can. With carbon K-rays, the transmittance to the living body is high, and the internal structure of the sample can be observed even with a thick sample. This is particularly effective for CT imaging. On the other hand, when observed in the “water window” region, which has an energy higher than that of carbon K-rays, the transmittance with respect to carbon is lowered. Therefore, it is necessary to remove X-rays exceeding 282 eV as much as possible. In this case, X-rays of 287 eV or more can be selectively removed by observing using the first state. Thus, by using two condensing optical systems, more information can be obtained compared to the X-ray imaging apparatus of the comparative example using one condensing optical system, which is highly useful.

DESCRIPTION OF SYMBOLS 1 ... X-ray source, 2 ... Filter, 3A-3D ... Condensing optical system, 4 ... Shielding member (1st shielding member), 5 ... Shielding member (2nd shielding member), 6 ... Imaging optical system, 7 ... Detector: 8 ... Control unit, 10A to 10C ... X-ray imaging device, 15 ... Shielding member (third shielding member), 16 ... Shielding member (third shielding member), 31 ... First optical element, 32 ... Second Optical element, 31c: first reflecting surface, 32c: second reflecting surface, 61c: reflecting surface (third reflecting surface), A: reference line, C1, C2: optical axis, S: sample.

Claims (9)

An X-ray source that emits X-rays applied to the sample;
A detector for detecting X-rays from the sample;
A collector having a first reflection surface and a second reflection surface, which are arranged on a reference line from the X-ray source to the detector and collect the X-rays emitted from the X-ray source on the sample by total reflection. Optical optics,
An imaging optical system disposed on the reference line and imaging the X-rays from the sample on the detector;
The state of the condensing optical system includes a first state in which X-rays totally reflected by the first reflecting surface are condensed on the sample, and an X-ray totally reflected by the second reflecting surface on the sample. A control unit that performs control to switch between the second state to be condensed; and
With
The sample is held at a predetermined distance from the X-ray source on the reference line,
An angle formed between the first reflective surface and the reference line and an angle formed between the second reflective surface and the reference line are different from each other.
The angle formed between the optical axis of X-rays totally reflected by the first reflecting surface in the first state and the reference line, and the optical axis of X-rays totally reflected by the second reflecting surface in the second state And the angle formed by the reference line is equivalent to each other,
X-ray imaging device. The condensing optical system includes a first optical element including the first reflecting surface, a second reflecting surface, and the first optical element in a state aligned with the first optical element along the reference line. An integrated second optical element;
The X-ray imaging according to claim 1, wherein the control unit switches the first state and the second state by moving the first optical element and the second optical element along the reference line. apparatus. The condensing optical system includes a first optical element including the first reflecting surface, and a second optical element including the second reflecting surface and configured separately from the first optical element,
The X-ray imaging apparatus according to claim 1, wherein the control unit switches between the first state and the second state by moving the first optical element and the second optical element. A first shielding member for shielding X-rays from the X-ray source toward the second reflecting surface;
A second shielding member for shielding X-rays from the X-ray source toward the first reflecting surface;
With
The controller is configured to shield the X-ray from the X-ray source toward the second reflecting surface using the first shielding member, and the first reflection from the X-ray source using the second shielding member. The X-ray imaging apparatus according to claim 1, wherein the X-ray imaging apparatus switches between the first state and the second state by selecting any one of states in which X-rays directed toward the surface are shielded.   5. The X-ray imaging according to claim 1, wherein the imaging optical system includes a third reflecting surface that totally reflects X-rays from the sample and forms an image on the detector. apparatus.   The X-ray imaging apparatus according to claim 5, wherein the third reflecting surface totally reflects X-rays in a total energy region totally reflected on the first reflecting surface and the second reflecting surface. A filter that is disposed on the reference line and removes X-rays on the low energy region side of the X-rays of the energy region that is totally reflected on the first reflecting surface and the second reflecting surface;
The X-ray imaging device according to any one of claims 1 to 6.   The X-ray imaging apparatus according to claim 1, further comprising a third shielding member that is disposed on the reference line and shields X-rays that enter the detector without passing through the condensing optical system. . An X-ray imaging method using the X-ray imaging apparatus according to claim 1,
A selection step of selecting whether the state of the condensing optical system is the first state or the second state by the control unit;
An emission step of emitting X-rays irradiating the sample from the X-ray source;
A condensing step of condensing the X-rays emitted in the emitting step onto the sample by the condensing optical system;
An imaging step of imaging X-rays from the sample on the detector by the imaging optical system;
A detection step of detecting, by the detector, the X-rays imaged in the imaging step.

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